Natural Gas is comprised of a mixture of gases (See API 14.1 Section 6.3 and naturalgas.org). Natural gas is bought and sold based on its heating value (BTU), which is derived from a compositional analysis of the natural gas. It is the BTU content that determines the monetary value of a given volume of natural gas. This BTU value is generally expressed in decatherms (one million BTU).
To determine the total heat value of a given volume of gas, a sample of the gas is analyzed, and from the compositional data, its heat value per unit volume is calculated. This value is generally expressed in BTU/cu ft. The typical range of transmission quality gas ranges between 1000 and 1100 BTU/cu ft. Production gas, storage facility gas, NGL, and new found Shale Gas can have much higher heating values up to or even exceeding 1500 BTU/cu ft.
There has been a long-standing controversy between gas producers and gas transporters regarding entrained liquid typically present in most high BTU/cu ft. gas (rich or “wet” gas). Transporter tariffs require essentially liquid-free gas. Liquid in the gas being transported causes operational and safety problems. The practice is to separate the liquid before entering a transport (pipe) line.
The API 14.1 standards (Manual of Petroleum Measurement Standards, 2006) scope does not include supercritical fluid (dense phase) or “wet gas” “(a term referenced by the Natural Gas industry as a gas that is at or below its hydrocarbon dew point temperature and/or contains entrained liquid), nor does the GPA 2166 standard (Obtaining Natural Gas Samples for Analysis by Gas Chromatography, 2005). In summary, there is no known standard which defines how to obtain a “representative sample” of a natural gas supply having entrained liquid in any form.
Therefore, to fully comply with the current industry standards, membrane-tipped probes such as the A+ Corporation Genie Probe (see U.S. Pat. Nos. 6,357,304, 6,701,794, 6,904,816, 7,004,041, and 7,134,318) have been used for many years to shed entrained liquids inside pressurized pipelines. Electrically powered heaters may be provided, which are powered by a separate power line included in the tube bundle. This power line is separate from the heat trace.
Companies such as Mustang Sampling, LLC have bolted enclosures to the A+ Corporation membrane-tipped probes, and are believed to utilize third party, electrically-powered heater blocks and A+ Corporation cartridge-type heated regulators for the enclosure, as well as third party electrical heat trace products. See for example U.S. Pat. No. 7,162,933. See also U.S. Pat. No. 9,459,185 relating to a solar powered sample analyzing system. See also ABB NGC8206 User Manual, Copyright 2009, Pages 1-17 and 2-58 through 2-64, available for download at their website.
Other housing or enclosure providers include, for example, vendors such as Intertec Hess GmbH's instrumentation component offerings on the internet at www.Intertec.info—Intertec Hess is not only a provider of enclosures but is also a provider of the electrically-powered heater blocks. Splicing kits suitable for such an application may be found at Protherm Industries Inc website, which offers, for example, a FE Series Splice Kit which could be used in this application; splice kits also available from other third party providers such as Pentair at their website.
Mustang Sampling, LLC Brochures MSB-PONY and MSB P53, available at their website, can include products incorporating A+ Corporation Genie membrane tipped probes, and utilize third party, electrically-powered heater blocks and A+ Corporation cartridge-type heated regulators and third party heat trace, as described above. Mustang Sampling brochure MSB P53 illustrates a product which can include A+ Corporation GENIE brand membrane separators (U.S. Pat. No. 7,555,964, a CIP of U.S. Pat. No. 7,097,693 (listing the present Inventor as second Inventor)) in an enclosure, which is ideally mounted in the vicinity of the analyzer, which may include additional electrically-powered heater blocks and electrically powered heated regulators (See Mayeaux U.S. Pat. No. 6,357,304, Thompson U.S. Pat. No. 7,162,933, and Thompson US 2012/0325694 A1).
Other companies such as Welker Engineering use non-membrane probes (fixed probes) and bring the liquids outside the pipeline to reject the liquids inside enclosures containing an electrically powered heated regulator and then returning the liquid back to the pipeline, while hanging a hinged enclosure onto the probe (see Welker SCHS manual, page 6, at their website, and U.S. Pat. No. 7,471,882). The purpose of these sample systems is to reject entrained liquids and maintain the sample system temperature above the sample dew point to prevent further condensation.
The above and other known prior art rely upon power being readily available for electrical cartridge heater devices and electrical heater blocks to provide heat for the sample systems, or vacuum jacketed tubing that has been used commercially for liquified natural gas sample systems for decades. Vacuum jacketed tubing providers include companies like Acme Cryogenics and Cryofab. Also see Thompson U.S. Pat. No. 9,395,280 B2.
Recently the Bureau of Land Management (BLM) has revised 43 CFR 3175 (Order 5) The Onshore Oil and Gas Operations, Federal and Indian Oil and Gas Leases, Measurement of Gas effective Jan. 17, 2017, as indicated in the Federal Register, Vol 81, No 222, Sections 3175.111 and 3175.112, pages 81578-81580, issued 17 Nov. 2016.
Sections 3175.111 and 3175.112 now mandate a sampling protocol that is outside of the scope of API 14.1 and GPA 2166, by mandating sampling of two-phase samples (gas with entrained liquids) without rejecting the liquids, to provide a sample to the analyzer. The new BLM order tries to reference parts of API 14.1 and GPA 2166, but it is clearly outside the scope of both of those industry standards. In addition, the new BLM order forbids the use of membranes or any other type of filter and means of liquid rejection in the probes used to take the sample. Therefore, contaminants like glycols and amines will no longer be rejected, filtered, or removed from the sample that is taken from the pipeline. The new order requires liquids and gases to be removed from the center third of the pipeline and heated sample lines to vaporize any liquids removed before they reach the analyzer.
Many of these sample points are in small diameter pipelines with limited electrical power available, or only low wattage close proximity solar power available. Solar power has been traditionally used in natural gas sampling for decades. See U.S. Pat. No. 5,501,080A, McManus et al, claiming a 1994 Priority date as one example as well as Thompson U.S. Pat. No. 9,459,185 and vendors such as ABB (See the ABB NGC8206 user manual pages 1-17 and 2-58 through 2-64, copyright 2009, available at the company website).
Most of the BLM sample points will only have solar power available for the short distance of self-limited heat trace tubing, but will be required to heat and vaporize the samples. Many of these BLM regulated locations will utilize portable low power gas analyzers that are powered from the technician's vehicle instead of on-site stationary conventionally powered gas analyzers such as gas chromatographs or other types of gas analyzers.